Current development in advanced wireless communication has led to the requirement of high spectral efficiency and reliable communication. Unfortunately, packet errors by fading channel environment and interferences originated from various sources make the capacity of overall system to be limited.
Hybrid Automatic Repeat Request (HARQ) which is ARQ protocol combined with Forward Error Correction (FEC) is strongly considered as one of cutting edge technologies for future reliable communication. The HARQ scheme can largely be classified into the type of two. One is HARQ-Chase Combining (CC) which is disclosed in D. Chase, Code Combining: A maximum-likelihood decoding approach for combining an arbitrary number of noisy packets, IEEE Trans. on Commun., Vol. 33, pp. 593-607, May 1985. The other scheme is HARQ-Increment Redundancy (IR). In the HARQ-CC, when a receiver detects an error through cyclic redundancy checking (CRC) while decoding the transmitted packet, the same packet with the same modulation and coding is sent to the receiver, repeatedly. Meanwhile, HARQ-IR retransmits different packets in order to achieve the coding gain, in which parity bits can be manipulated through puncturing and repetition.
Multiple Input Multiple Output (MIMO) systems are regarded as one of the most promising research areas of wireless communication. Spatial diversity provided by multiple antenna configurations for both transmitter and receiver is known to tremendously increase system capacity without additional bandwidth. As a result, various approaches have been studied to use the benefit of transmit diversity and received diversity.
Constellation Rearrangement disclosed by the PCT international application No. PCT/KR2007/003625 filed by this applicant provides additional gain through averaging the difference of inherent reliability between component bits.
There is a need to improve performance of system by applying constellation rearrangement to various schemes such as MIMO system, HARQ, multi-level modulation, etc.